88 Among all the Churches and Ecclesial Communities, the Catholic Church is conscious that she has preserved the ministry of the Successor of the Apostle Peter, the Bishop of Rome, whom God established as her "perpetual and visible principle and foundation of unity" and whom the Spirit sustains in order that he may enable all the others to share in this essential good. In the beautiful expression of Pope Saint Gregory the Great, my ministry is that of servus servorum Dei . This designation is the best possible safeguard against the risk of separating power (and in particular the primacy) from ministry. Such a separation would contradict the very meaning of power according to the Gospel: "I am among you as one who serves" ( Lk 22:27), says our Lord Jesus Christ, the Head of the Church. On the other hand, as I acknowledged on the important occasion of a visit to the World Council of Churches in Geneva on 12 June 1984, the Catholic Church's conviction that in the ministry of the Bishop of Rome she has preserved, in fidelity to the Apostolic Tradition and the faith of the Fathers, the visible sign and guarantor of unity, constitutes a difficulty for most other Christians, whose memory is marked by certain painful recollections. To the extent that we are responsible for these, I join my Predecessor Paul VI in asking forgiveness.
Source: Ut Unum Sint (Vatican.va)